Pathokiness mid2 questions

9. Describe what is meant by a force couple.

2 or more muscle forces directed in different linear directions producing rotation of a bone around a relatively fixed axis - the resulting torques are acting in the same rotatory direction

The nervous system activating the fewest muscle fibers possible for joint action or control is an example of the Law of Parsimony. TRUE False

True

6.What is the major benefit of having the extrinsic finger flexors and extensors cross more than one joint?

can produce greater force through a large ROM; helps control length-tension

1.How could you differentiate between limited range of motion in the humeroulnar joint from tightness of the biceps brachii muscle?

compare elbow extension ROM with shoulder in extension (biceps is fully stretched) to elbow extension ROM with shoulder in flexion (biceps slack, limiting factor will be elbow joint capsule or one joint mms of anterior elbow)

2. What tissue is unlikely to be injured following an anterior shoulder dislocation? a. Humeral head articular cartilage b. Middle glenohumeral ligament c. Inferior labrum d. Superior labrum

d

5. Demonstrate a position where contraction of the shoulder flexors (anterior deltoid, pectoralis major) could extend the elbow? (think closed chain)

a. In closed chain position with shoulder extended, contraction of the shoulder flexors will extend the elbow over a fixed hand - there are others too!

2. Estimate the differences in your total forearm rotation ROM in "proximal on distal" and "distal on proximal" pronation.

a. Proximal on distal pronation i. ~80-90º b. Distal on proximal pronation i. ~150º

7. Describe the 6 kinematic principles of shoulder abduction

a. Scapulohumeral rhythm (2:1 motion of GH to scapulothoracic)b. Upward rotation of scapula is a result of SC joint elevation and AC joint upward rotation c. Clavicle retracts at SC joint d. Scapula posteriorly tilts and ER e. Clavicle posteriorly rotates around its long axis f. Glenohumeral ER

3. List a likely antagonist for each of the following muscles if they were acting in an open kinematic chain.

a. Serratus Anterior rhomboids / trap b. Posterior Deltoid anterior deltoid / coracobrachialis c. Teres Minor pec major / teres major d. Pectoralis Minor upper trap / levator

7. Note the function (control of motion or stabilization) of each of the following ligaments.

a. coracoclavicular - conoid portion limits retraction, elevation of clavicle - trapezoid portion limits protraction, elevation of clavicle b. acromioclavicular stabilizes joint surfaces c. coracoacromial forms roof of coracoacromial arch, could prevent superior translation of humeral head

5. Paralysis of the trapezius can result in posterior shoulder instability of the glenohumeral joint. a. TRUE b. False

b

5. Draw a picture of the central pillar of the wrist from the lateral view (radius, lunate, capitate and 3rd metacarpal) in 3 situations: a. Normal alignment

b. DISI - what wrist ligament is likely ruptured? i. scapholunate

1. What tissue does not stabilize the sternoclavicular joint? a. Anterior and posterior sternoclavicular joint ligaments b. Interclavicular ligament

c. Coracoclavicular ligament d. Articular disc c

Pronator muscles produce about 25% greater isometric torque than the supinator muscles TRUE False

false

6. What motion increases tension in all parts of the inferior glenohumeral ligament?

i. Abduction

b. How might this differ if the injury was in the axilla?

i. Add elbow extensor weakness

Large Group Activity - Subacromial Impingement 1. See notes and text for what might contribute to subacromial impingment and why I refer to this as a continuum. 2. What do you think is the most common direction of GH dislocation (anterior,posterior, inferior)? Why is the GH joint inherently unstable in this position? What is the mechanism of this injury?

i. Anterior - poor anterior structural stability, long lever for external force to act upon - think throwing a football and someone tries to get the football and drives your outstretched arm backward - the humeral head would go forward into the area with poor anterior stability

5. How are the arthrokinematics of GH joint internal rotation from anatomic position different than with the arm abducted to 90 degrees?

i. Anterior roll, posterior slide ii. Primarily a spin of the humeral head on the glenoid fossa

3. How does the longhead of the biceps help the rotator cuff muscles?

i. Assists with humeral head depression

5. A patient has a 20-degree elbow flexion contracture that is assumed to originate from muscular tightness. As the clinician applies an extension stretch (torque) to the elbow near the end range of motion, the forearm passively "drifts" rather strongly toward supination. What clue does this observation provide as to which muscle or muscles are most tight (stiff)?

i. Biceps

4. What happens to grasp with a longstanding ulnar nerve injury?

i. Clawing of the hand, greater on the ulnar than radial side of the hand - inability to fully extend the MCPs and IPs without the intrinsics help with stopping the ED from hyperextending the MCPs and their important force in extending the IPs

5. Describe the movement of the 1st metacarpal on the trapezium during thumb flexion/extension, and abduction/adduction.

i. Concave on covex with flexion, convex on concave in abd/add

4. What are the CC ligaments in the shoulder complex?

i. Coracoclavicular, costoclavicular - don't get them confused!

8. Based on moment arm alone, which tissue shown in Fig. 6.17A could generate the greatest passive resistive torque opposing an elbow extension movement?

i. Dermis

6. Pick up something in the room (~5# or so) that requires you to flex your elbow with your forearm pronated, and then with your forearm supinated. What difference did you feel in biceps brachii activation in each position?

i. During active elbow flexion the biceps muscle activity is less with the forearm pronated than supinated

2. Palpate a partner's acromion, clavicle, SC, and AC joints. Describe the motions of the SC joint during scapular elevation, depression, protraction and retraction.

i. Elevation/Depression: Clavicle is convex, manubrium is concave ii. Protraction/Retraction: Clavicle is cancave, manubrium is convex

b. In what position would you place your shoulder (think rotation in the transverse plane) to get the LH of the biceps to best assist with shoulder abduction?

i. External rotation

What is a primary difference in the structure of the two muscles

i. FDP has 1 mm belly with 4 tendons and tendons cross DIP to flex distal phalanx. FDP. [FDP: proximal three-fourths of the anterior and medial sides of the ulna and adjacent interosseous membrane Distal attachments: by four tendons, each to the palmar base of the distal phalanges of the fingers Innervation: Medial half: ulnar nerve Lateral half: median nerve] ii. FDS has separate mm bellies / tendons which can act independent of one another and tendons do not cross DIP, but do cross PIP. [Proximal attachments: Humeroulnar head: common flexor-pronator tendon attaching to the medial epicondyle of the humerus and the medial side of the coronoid process of the ulna Radial head: oblique line just distal and lateral to the bicipital tuberosity Distal attachments: by four tendons, each to the sides of the middle phalanges of the fingers Innervation: median nerve]

6. The median nerve can be compressed by several different anatomical structures at the elbow (e.g., pronator teres, sublimis bridge/arch, lacertus fibrosis). Would you expect to see sensory loss with compression of the median nerve at these locations? If yes, where?

i. Hand only - median nerve distribution (palmar radial side, dorsal 2nd and 3rd digits)

4.a. Use a piece of theraband or a rope to represent the longhead of the biceps at your shoulder. Imagine a shortening contraction of the biceps brachii without flexing your elbow. What effect might this have on the humeral head as you elevate your arm?

i. Humeral head depression

c. Can you isolate the function of the superficialis from the profundus? If so, how?

i. Isolate FDS by flexing PIP while keeping DIP extended; isolate FDP by flexing DIP while keeping PIP extended (may need to passively hold PIP in extension)

3. Devise a stretch of the lumbrical muscles? Demonstrate it to your group.

i. Lumbrical action = MCP flexion, IP extension ii. To stretch, do the opposite - MCP hyperextension, IP flexion

a. Beginner Question—Which muscles/tendons intrinsic to the hand flex the MCP joints and extend the interphalangeal joints?

i. Lumbricals, interossei

c. VISI - what wrist ligament is likely ruptured?

i. Lunotriquetral

2. Explain how MCP flexion tightens the collateral ligaments. Use your own hand to convince yourself that this is indeed the case. What motions did you perform and in what position were your MCP joints?

i. MCP flexion limits abduction/adduction, MCP extension allows abduction/adduction - this is due to the cam shape of the metacarpal head. See picture.

3. Place your partner supine at the edge of the plinth. Have them relax while you take hold of their hand. Be sure they stay relaxed and then passively move their limb into complete abduction. Begin with their anterior surface of their brachium towards the ceiling. You must raise their limb just above the plinth to do this, but stay in the frontal plane of their body (not the scapular plane).2 a. What surface of their elbow is facing the ceiling at the end of abduction?

i. Medial

4. What motor and/or sensory function would be affected by a compression of the radial nerve as it enters the supinator muscle?

i. Motor loss of elbow and wrist/finger extension, sensory loss of posterior arm, radial dorsum of hand

d. Why are the wrist ligaments so important to wrist stability?

i. No muscles control only the wrist - they cross multiple joints, so ligaments are critical for stability (bony structure also is not very helpful for stability here)

b. Using the shoulder anatomical model, how might the coracoclavicular ligaments check these motions. (Look at the shoulder model to identify the conoid (medial) and trapezoid (lateral) portions of the ligament).

i. Note how the coracoclavicular ligaments check these motions. Conoid checks retraction; trapezoid checks protraction c.

4. Draw a picture of the PIP joints in flexion and in extension. Show how the volar or palmar plates both limit hyperextension and increase the articular surface for extension. Also, show what happens to the volar plates in full flexion.

i. Note how the volar plate almost folds on itself in flexion ii. Note how the volar plate will get tight and prevent too much hyperextension but also (in blue) actually increases the articular surface of the joint so that it can hyperextend some and maintain an articulation

Finally, what would tightness in the coracoclavicular ligaments do to the clavicle?

i. Posterior rotation

1.a. Using figure 5.4 from Neumann and the skeleton model, speculate how the angle between the clavicle and the scapula changes with retraction and protraction of the shoulder girdle (use the interior angle as your reference).

i. Rest ~60º ii. Retraction increased angle iii. Protraction decreased angle

Large Group Activity1. How do monoarticular muscles enhance force output in biarticular muscles; using the elbow and shoulder as an example. Also, scapulohumeral rhythm.

i. Review this in the book/lectures

7. The ulnar nerve is perhaps the most common nerve compression at the elbow. What motor and sensory loss would you expect with a compression of the ulnar nerve at the cubital tunnel?

i. Sensory loss or numbness/tingling the 4th and 5th digits, the ulnar side of the dorsum of the hand and the hypothenar eminence, weakness of most hand intrinsics (except radial lumbricals)

2. How are the motions of the thumb different than those of the fingers? 3. How important is sensation in the hand?

i. Skin sensory function, joint receptors and muscle receptors are all important for normal function in the hand

How many nerves innervate the primary muscles that flex the elbow 1 2 3 4

3

b. With the back of your left hand on a table, immobilize your left ring finger in complete MCP, PIP, and DIP extension while you flex your index, long and little MCPs with your right hand. Try to flex your index, long, and little finger PIPs and DIPs in this position. What happened at the PIPs, and why?

Flexion

2.How does the position of the distal portion of the humerus act as an anatomic pulley for the triceps muscle? How does it affect triceps function?

In elbow flexion, the triceps tendon is pulled via attachment to olecranon around the distal end of the humerus. This increases the length of the mm/tendon (avoids active insufficiency), but decreases the moment arm (decreased torque for a given mm force).

b. Relate this to performing open chain isokinetic knee flexion and extension or using a leg press to rehabilitate the quadriceps muscle group.

Increased total lower extremity mm activity with leg press vs. isokinetic flex/ext greater isolation of quads with open chain extension vs. leg press

6. Why might you have an increased amount of glenohumeral external rotation with your shoulder abducted to 90° as compared to abducted to 30°?

Less muscular restraint at 90 degrees of abduction

2. a. List the muscles whose line of pull could produce an inferior glide of the head of the humerus on the surface of the glenoid fossa.

Subscapularis, infraspinatus, teres minor, long head of biceps, teres major, pectoralis major, latissimus dorsi

4. Trapezius and serratus anterior work synergistically during upward rotation of the scapula. a. TRUE b. False

a

What muscle is the most direct antagonist to the brachialis muscle? a.Medial head of the triceps b.Anconeus c.Long head of the triceps d.Posterior deltoid

a

3. What is an unlikely reason the supraspinatus is vulnerable to excessive wear over time? a. It must produce large internal forces, even during routine activities b. The muscle has an internal moment arm for shoulder abduction of about 2.5 cm during abduction c. The tendon has a reasonable blood supply to repair micro-tearing

d. Experiences repeated impingement against the coracoacromial ligament, the acromion, or the rim of the glenoid fossa c

What position of the upper extremity maximally elongates the biceps brachii muscle? a. Shoulder extension, elbow extension, and forearm pronation b. Shoulder extension, elbow extension, and forearm supination c. Shoulder extension, elbow flexion, and forearm pronation

d. Shoulder flexion, elbow extension, and forearm pronation a

3. What is the purpose of the sheaths that surround the flexor tendons of the fingers?

decrease friction during tendon gliding; prevent "bowstringing" of flexor tendons (maximizes length-tension relationship throughout a large ROM)

c. What happens to the PIP joint when the central tendon (slip) of the ED is cut?

i. The PIP remains flexed because there is no tension on the dorsum of the of the PIP. With longstanding PIP flexion, the volar plate is on slack and it may become adaptively shortened and create a PIP flexion contracture d. Expert Question--Explain how the lumbrical's design is suited to relax its own antagonist? i. This muscle originates off a tendon (FDP). When the lumbrical shortens it pulls the FDP tendon distally, thus relaxing the FDP - making it incapable of flexing the DIP

b. Intermediate Questions— True or False: The anatomical region called the "extensor expansion" is a bit of a misnomer.

i. True - action of the extensor expansion flexes the MCP, extends the IPs - so it does both

6. What ligament is injured with a "skiers thumb" injury? What joint is most affected?

i. Ulnar collateral ligament of the MCP

5. Lateral epicondylitis is sometimes treated with a compression strap over the proximal end of the wrist extensor muscles. If the problem were instead, a radial nerve compression, what might you expect with the patient's symptoms if you apply a compression strap?

i. Worsening of symptoms

3.a. What motor and/or sensory function would be affected by a compression of the radial nerve at the spiral groove of the humerus?

i. Wrist and finger extension weakness

c. Would this impact a patient's ability to drive a screw into a wall like in figure 6.45 in the text

i. Yes, triceps is necessary to neutralize the biceps elbow flexion activity when using the biceps as a supinator

3. With an eraseable marker, have one of your partners mark the following landmarks on their arm. a. axis of pronation/supination on the anterior side of your arm

i. axis runs obliquely across the forearm from radial head to ulnar head

c. Why is this necessary?

i. clear the greater tuberosity out from under the acromion to allow it to pass under the acromion with elevation

1. Analyze the motion of pronation from a "proximal on distal" perspective. Note which bones are moving and which bones are stationary. Compare that with an open chain pronation. What are the differences in the arthrokinematics between the two scenarios?

i. closed chain: ulna moves on radius ii. open chain: radius moves on ulna

2. In what position would you place your arm if you were to maximally stretch your brachialis muscle without interference from a potentially tight biceps muscle.

i. extend elbow with shoulder flexed (shoulder flexion puts biceps on slack, so it will not interfere with elbow ext)

6. Perform a seated press up. Draw a free body diagram representing elevation of the thorax on the fixed scapula and arm. Include vectors representing the latissimus dorsi, lower trapezius and pectoralis minor muscles. 3

i. lats attach to the humerus, so can indirectly apply a downward force to the scapula; lower trap and pectoralis minor can also apply a downward force to the scapula (or, as pictured above, these muscles will produce an upward force on the trunk if the humerus and scapula are stable)

b. add the 'ideal line of force' of a muscle that would pronate the forearm relative to this axis

i. mm force line perpendicular to this axis would be most effective pronator

c. Compare that line of force with that of the pronator teres and pronator quadratus

i. pronator quadratus is in best position to pronate the forearm (it also compresses the distal RU joint); the pronator teres can pronate, but also longitudinally compresses the forearm

c. What is the difference and why?

i. shoulder ER limits the forearm motion in closed chain forearm rotation

b. Considering that this was a passive movement on the part of your partner, what do you think may have caused the change from the start to end position above?

i. tautness in joint capsule / ligaments (twisting of soft tissue structures)

4. Palpate your distal R/U joint during a pronation and supination motion. In a pronated position, place your finger on the ulnar head. Leave your finger there as you slowly supinate the forearm. Describe what you are feeling as you go from full pronation to full supination.

i. ulnar head 'disappears 'with supination 2

What happened at the DIPs, and why?

ii. No flexion at DIPs 2º have immobilized DIP of ring finger so FDP contraction is limited and you are unable to flex the other DIPs independently

What muscle activity at the shoulder and the elbow is critical to making this happen?

iii. infraspinatus, pronator quadratus

10. a. Asking a patient to grasp a handle on a pulley weight system or attaching a cuff from the pulley weight system to their wrist will require different total muscular activity of the upper extremity. Based on this fact, why might you choose to do one or the other?

increased mm activity with grasping handle vs. using wrist cuff greater isolation of proximal mms with using wrist cuff vs. grasping handle

1.During abduction of the humerus, what force keeps the humeral head from rolling superiorly off the glenoid fossa?

inferiorly directed force of rotator cuff

During abduction of the humerus, what force keeps the humeral head from rolling superiorly off the glenoid fossa?

inferiorly directed force of rotator cuff

5. Describe how the longhead of the biceps brachii can act as a humeral depressor.

it can depress the humeral head via its attachment to the superior glenoid recognize that this occurs even more when the arm is ER, so that the LH of the biceps makes a significant contribution to the arthrokinematics of shoulder abduction

4. Describe both the kinematics and the muscle function that occur in a closed kinematic chain depression of the shoulder girdle (a press up from the seated position).

kinematics: depression, downward rotation, adduction of scapula active mms: pec minor, pec major, serratus ant, traps, rhomboids, teres major, lats

5. What symptoms would you expect to see with edema in the carpal tunnel and why?

median n sxs/signs: parasthesias / pain in median n distribution (radial ½ of palm and 1st 3-4 fingers - not the little finger); may have decreased fine motor ability, decreased strength in 1st 2 lumbricales and thenar mms

b. Which of the above muscles actively participate with the humeral elevators during elevation of the arm above the head?

subscapularis, infraspinatus, teres minor (and long head of biceps if shoulder is in ER)

4. What is the function of the interosseous membrane at the elbow?

transmits forces from distal radius to proximal ulna, prevents superior displacement of radius on ulna with WB through hand

8. What muscles stabilize the scapula on the thorax?

traps, levator, rhomboids, serratus ant, pec minor